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Search Results: 1 - 10 of 227854 matches for " Joel R. Peck "
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Hidden Epistastic Interactions Can Favour the Evolution of Sex and Recombination
Joel R. Peck, David Waxman, John J. Welch
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048382
Abstract: Deleterious mutations can have a strong influence on the outcome of evolution. The nature of this influence depends on how mutations combine together to affect fitness. “Negative epistasis” occurs when a new deleterious mutation causes the greatest loss in fitness in a genome that already contains many deleterious mutations. Negative epistasis is a key ingredient for some of the leading hypotheses regarding the evolution of recombination, the evolution of sex, and a variety of other phenomena. In general, laboratory studies have not supported the idea that negative epistasis is ubiquitous, and this has led to doubts about its importance in biological evolution. Here, we show that these experimental results may be misleading, because negative epistasis can produce evolutionary advantages for sex and recombination while simultaneously being almost impossible to detect using current experimental methods. Under asexual reproduction, such hidden epistasis influences evolutionary outcomes only if the fittest individuals are present in substantial numbers, while also forming a very small proportion of the population as a whole. This implies that our results for asexuals will apply only for very large populations, and also limits the extent of the fitness benefits that hidden epistasis can provide. Despite these caveats, our results show that the fitness consequences of sex and recombination cannot always be inferred from observable epistasis alone.
Fabrication and Corrosion Behaviour of Aluminium Alloy (LM-13) Reinforced with Nano-ZrO2 Particulate Chilled Nano Metal Matrix Composites (CNMMCs) for Aerospace Applications  [PDF]
Joel Hemanth, M. R. Divya
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.67015
Abstract: This research presents the results obtained and the discussions made from a series of corrosion experiments involving aluminum alloy (LM 13) reinforced with Nano-ZrO2, size of the particles dispersed varies from 100 - 200 nm and amount of addition varies from 3 wt% to 15 wt% in steps of 3 wt%. The resulting CNMMCs are solidified under the influence of copper chill of 25 mm thickness to study the effect of corrosion behavior. The corrosion test employed was the electrochemical polarization method according to ASTM G59-97 (2009) standards. Corrosion resistance was found to increase significantly with increase inZrO2 content in chilled CNMMCs. Nevertheless, even with high ZrO2 content corrosion attack i.e., pitting was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages, due to the formation of an adherent protective layer on the CNMMCs developed. SEM studies of the corroded surface were also examined to study the mechanism of corrosion. Present research is undertaken to develop a corrosion resistant composite for aerospace application where aluminum is highly suspected to corrosion.
On the Edit Distance of Powers of Cycles
Zhanar Berikkyzy,Ryan R. Martin,Chelsea Peck
Mathematics , 2015,
Abstract: The edit distance between two graphs on the same labeled vertex set is defined to be the size of the symmetric difference of the edge sets. The edit distance function of a hereditary property $\mathcal{H}$ is a function of $p\in [0,1]$ that measures, in the limit, the maximum normalized edit distance between a graph of density $p$ and $\mathcal{H}$. In this paper, we address the edit distance function for $\mbox{Forb}(H)$, where $H=C_h^t$, the $t^{\rm th}$ power of the cycle of length $h$. For $h\geq 2t(t+1)+1$ and $h$ not divisible by $t+1$, we determine the function for all values of $p$. For $h\geq 2t(t+1)+1$ and $h$ divisible by $t+1$, the function is obtained for all but small values of $p$. We also obtain some results for smaller values of $h$.
Determining the Authenticity of Artifacts by Oxygen Isotope Analysis  [PDF]
Joel Kronfeld, Amnon Rosenfeld, Howard R. Feldman
Open Journal of Geology (OJG) , 2013, DOI: 10.4236/ojg.2013.34036
Abstract:

A technique used to determine the authenticity of artifacts that compares the oxygen isotopic composition of speleothems to the carbonate included within the patina of unprovenanced artifacts is of questionable value. The unprovenanced Jehoash Inscription Tablet and James Ossuary are of potentially immense historical and cultural importance. Nevertheless, they both were rejected by workers based on the oxygen isotope technique which provided the major foundational evidence of forgery in the longest running archaeological trial in Israel. Nevertheless, both these artifacts were determined not to be forged. The initial incongruence between the oxygen isotopes of the speleothems of the Soreq cave (Israel) purported to represent the unique composition of Jerusalem rainfall, and the patina on the artifacts, can be readily explained by the accretion of materials and geo-biochemical processes expected in normal patina formation in the Jerusalem region. The patina formation involves sporadic events in disequilibrium kinetic processes that are opposed to the equilibrium formation of speleothems in a sealed cave. Moreover, 23 of 56 patina samples (41%) on well-documented ancient artifacts from Israel yielded oxygen isotope values greater or lower than the expected speleothem values of -4 δ18O ‰ [PDB] to -6 δ18O ‰ [PDB]. Thus, the speleothem-patina correlation is invalid and the applied oxygen isotopes technique for determining the authenticity of patinas on artifacts is not a useful tool in the authentication of artifacts.

Another Look at Becker’s Irrational Consumer  [PDF]
Richard M. Peck
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23047
Abstract: Becker’s paper \"Irrational Consumers and Economic Theory\" ([1]) is a classic. This paper shows how to parameterize the process of selecting points randomly on a budget set. This parameterization also simplifies the proof that average demand curves are downward sloping and satisfy the weak axiom of revealed preference. In addition, we show that the probability distribution of random choices does not need to be restricted to a uniform distribution which Becker assumes. In fact, the distribution can be arbitrary.
Experimental Study of a Lorentz Actuated Orbit
William R. Gorman,James D. Brownridge,Mason Peck
Physics , 2008,
Abstract: This experimental study investigates a new technique to keep a satellite in orbit utilizing electrodynamics. The technique consists of establishing a charge on a satellite such that the body's motion through a planetary magnetic field induces acceleration via the Lorentz force. In order to find the relationship between capacitance and power required to balance incident plasma current, various objects were tested in high vacuum, plasma, and Xenon gas to determine their ability to hold charge. Radioactive material (Am-241) and pyroelectric crystals were tested as a candidate power source for charging the objects. Microscopic arcing was observed at voltages as low as -300 V. This arcing caused solder to explode off of the object. Insulating the object allowed the charge to remain on the object longer, while in the plasma, and also eliminated the arcing. However, this insulation does not allow a net charge to reside on the surface of the spacecraft.
Algumas memórias do cinema cubano mais polêmico
Río, Joel del;
Estudos Avan?ados , 2011, DOI: 10.1590/S0103-40142011000200013
Abstract: since the cuban institute of cinematographic art and industry (icaic) was founded in 1959, a series of films have been made that highlighted social polemics and lashed out against the errors of socialism in cuba. this essay intends to analyze the main vectors of thought that underlay some of these controversial films (both documentaries and fiction), in particular their character of being faithful mirrors of reality. it also attempts to show the vertical commitment to reality and its everyday dilemmas that characterize the best cuban films - that is to say, the most controversial cuban films -, which are supported by institutional policies that consistently nurture the artistic and social relevance of a non-conformist cinema that criticizes, questions and is intimately committed to the collective quest for a more just, egalitarian and humanistic society. from pm to fresa y chocolate, un día de noviembre and papeles secundarios, the essay strives to interpret the nuances of each controversy, while describing the contributions of such films to the medullar energy of the cuban culture.
Cefalalgias
Joel R Saper
Revista Cubana de Medicina , 2001,
Abstract:
Edipo: mito fundacional de los Estados imperiales
Joel Flores R.
Política y cultura , 1995,
Abstract:
States and Internet Enforcement
Joel R. Reidenberg
University of Ottawa Law and Technology Journal , 2003,
Abstract: [Abstract] This essay addresses the enforcement of decisions through Internet instruments. Traditionally, a state's enforcement power was bounded by territorial limits. However, for the online environment, the lack of local assets and the assistance of foreign courts no longer constrain state enforcement powers. States can enforce their decisions and policies through Internet instruments. Online mechanisms are available and can be developed for such pursuits. The starting point is a brief justification of Internet enforcement as the obligation of democratic states. Next, the essay describes the movement to re-engineer the Internet infrastructure by public and private actions and argues that the re-engineering facilitates state enforcement of legal and policy decisions. The essay maintains that states will increasingly try to use network intermediaries such as payment systems and Internet service providers as enforcement instruments. Finally and most importantly, the essay focuses on ways that states may harness the power of technological instruments such as worms, filters and packet interceptors to enforce decisions and sanction malfeasance.*****[Résumé] Cet article traite de l’exécution de jugements à l’aide de ressources Internet. Traditionnellement, un état exer ait son pouvoir d’exécution à l’intérieur de ses limites territoriales. En ligne, par contre, l’absence d’éléments d’actif locaux et l’aide des tribunaux étrangers ne constituent plus des limites aux pouvoirs d’exécution d’un état. Les états peuvent exécuter leurs décisions et leurs politiques au moyen de ressources Internet. Des mécanismes sont disponibles en ligne et peuvent être développés à cette fin. L’article justifie brièvement l’exécution par Internet, la présentant comme une obligation des états démocratiques. Il décrit ensuite le mouvement de réforme de l’ingénierie de l’infrastructure Internet par des actions publiques et privées, soutenant que cette réforme facilite l’exécution des décisions juridiques et politiques. L’article allègue que les états chercheront de plus en plus à utiliser les intermédiaires réseau, tels que les systèmes de paiement et les fournisseurs d’Internet, en tant que ressources pour l’exécution de jugements. Enfin, ce qui est plus important encore, l’article scrute comment l’état peut exploiter le potentiel des ressources technologiques, comme les vers, les filtres et les intercepteurs, pour l’exécution de décisions et la sanction de méfaits.
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